special sense Flashcards
receptor cells make up…
- Neuroepithelium: retina and olfactory Epithelium, sensory Neurons from neuroectoderm
- Sensoepithelium: taste buds and Epithelium in internal ear, Special epithelial cells from Surface ectoderm
- Sensory nerve ending (pacinian and Meisners corpuscle)
Ocular refractive media consists of
lens, chamber, vitreous humor
Accessory structures
eyelids, lacrimal Glands, extraocular muscles, conjunctiva
Developmental Sources of the eye
- Neural tube: retina, muscle of Iris
- Surface ectoderm: lens, anterior Epithelium of Cornea
- Head Mesenchyme: all others
Development of eye
3rd week:
- outpockenings –> vesicles attached by optic stalk –> optic Cup –> inner layer (muscle of Iris, neural of retina) and outer layer (Pigment of retina)
- lense Surface ectoderm –> lens placode –> lens vesicle –>lens
- optic stalk –> otpic nerve
6th week:
- hyaloid artery into optic Cup –> choroid fissue that Closes befire birth
Wall of the eyeball
FIBROUS LAYER
- Cornea
- sclera
VASCULAR LAYER
- Iris
- ciliary Body
- choroid
RETIANL LAYER
Cornea
avascular!!
- Stratified squamous non-keratinized Epithelium
- Anterior b.m. (bowman’s membrane)
- Stroma of dense collagenous tissue in lamellae
- Posterior b.m. (descemet’s membrane)
- Pre-Descemet’s membrane (Dua’s layer)
6- Endothelium
Sclera
- irregular dense collagenous tissue
- Collagen fibers and elastic fibers
- blood vessels and nerves
Cornoscleral Limbus: Junction of Cornea and sclera, canal of Schlemm
iris
- highly vascularized
- non-photosensitive retina on posterior Surface
sphincter pupillae muscle: smooth muscle cells near margin of Iris
dilator pupillae muscle: extends radially, composed of the processes of myoepithelial cells
Ciliary body
- smooth muscles
- inner Surface covered by non-photosensitive retina
Choroid
- pigmented loose CT
- absorbs light
- provides support and nutrients for retina
Parts of the retina
Photosensitive
Non-photosensitive
- iridial part (behind Iris)
- ciliary part (behind ciliary Body)
ora serrata: line between photosensitive and non-photosensitive retina
Microscopic structure of the retina
two layers:
- outer layer
- inner layer
Iridial part of the non-photosensitive retina
outer layer:
- 1 layer of pigmented myoepithelial cells (dilator pupillae muscle)
inner layer:
1 layer of pigmented cells
- -> Formation of dilator pupillae
- -> absorption of light
Ciliary part of non-photosensitive retina
outer layer:
1 layer of pigentocyti
inner layer:
1 layer of non-pigmented cuboidal cells
- ->Secretion of aqueous Humor
- ->Production of zonular fibers –> suspensory ligament of lens
Photosensitive retina is divided in:
outer layer
inner layer
Pigmented (outer) layer of photosensitive retina
- retinal pigement Epithelium (single layer of Pigemtocyti)
- Basement membrane
pigentocyti have microvilli on inner sruface that go between photoreceptors
Functions of retinal pigemtn epithelium
- absorbs light
- structural support
- metabolic support
- blood- retinal-barrier
- phagocytoses membranous Disc
- (re) Synthesis of rhodopsin
(Re) Synthesis of rhodopsin
Vitamin A –> Retinol –> retinal
retinal + opsin –> rhodopsin
Neural (inner) layer of photosensitive retina (Groups of Neurons)
Photoreceptor cells
Conducting cells
Ganglion cells
Photoreceptor cells are divided in:
rod cells
Cone cells
Structure of photoreceptor cells
bipolar Neurons
dendrite Body axon that Ends in: - sferule (rod) - pedicle (cone)
Dendrite of photoreceptor cell
- outer Segment
- Connecting cilium
- inner Segment
>outer part (mitochondria)
>inner part (Rhodopsin is synthesized)
Outer Segment of rod
- stack of flattened membranous Discs
- Discs are shed and phagocytosed by RPE
- light: retinal –> Retinol , release of opsin and changes in permeability of Plasma membranes
Functions of rods
- more sensitive to light
- during period of low light intensity –> Image of gray tones
Outer Segment of cone
- memranous Disc are continuous with Plasma membrane
three classe sof cones
L (Long) M (middle) S (short-wavelength)
Function of cones
- sensitive to red, green and blue regions of visual spectrum
Conducting cells of the retina
- bipolar cells
- horizontal cells
- Amacrine cells
Bipolar cells
Connections:
- photoreceptors and Ganglion cells
- photoreceptors and horizontal cells
- photoreceptors and amacrine cells
Horizontal cells
- connect rods and cones
- Synapse with bipolar cells
Amacrine cells
- no not have an axon!!!
- connect bipolar and Ganglion cells
Ganglion cells
- large, mulitpolar Neurons
- with bipolar cells
- with few amacrine cells
- axons pass into optic nerve Fiber layer and then to optic nerve
Supporting cells of the retina
Müller cells: type of astrocytes
- apical Ends form outer limiting membrane
- Basic parts together with b.m. form inner limiting membrane
functions: support, Transfer of metabolites, Regulation of electrolytes
10 histological layers of retina (PPOOOIIGLI)
1: Pigmented layer: RPE
2. Photoreceptor layer: outer and inner Segments
3. Outer limiting layer: apical Ends of Mülller cells
4 . Outer nuclear layer: cell bodies of photorecept,
5. Outer plexiform layer: processes of photo, horizontal and bipolar
6. Inner nuclear layer: cell bodies of conducting and Müller
7. Inner plexiform layer: processes of bipolar, amacrine and ganglion
8. Ganglion cell layer: cell bodies of ganglion
9. Layer of optic nerve fibers: axons of glangion cells
10. Inner limiting membrane: Basic Ends of Müller cells
Optic disc
- where fibers of Ganglion cells converge
- blood vessels pass through Center
- axons of Ganglion cells are not myelinated except here
Macula lutea
- near optic axis of the eyeball
- there is a Fovea in the middle
- Fovea is most sensitive area, because
>lacks bloos vessels
>contains only cones
>Monosynaptic Connections between the neurons
Monosynaptic connections
- Ratio between cones, bipolar cells, Ganglion cells
1: 1:1 - only in macula lutea
Inverted eye
Photoreceptor dendrites are directed to choroid, not to light
Olfactory mucosa layers
Olfactory Epithelium
Lamina propdia mucosae
Olfactory epithelium
Pseudostratified epitheliem with:
- olfactory cells
- supporting cells
- Basal cells
Olfactory cell
- bipolar Neurons
- dendritic processes Project above epitheium and make olfactory knob with cilia
- Plasma membrane of cilia contains odorant-binding proteins
- Long axon leaves Epithelium
- can regenerate
Supporting cell in olfactory epithelium
- tall columnar
- microvilli on apical Surface
. Metabolic and mechanical support - synthesize and secrete odorant binding proteins
Lamina propria mucosae in olfactory epithelium
loose CT
+ olfactory (Bowman’s) Glands
–> branched tubuloalveolar Glands –> deliver secretions
serour secretion is trap for odoriferous substances
Ear is divided into:
External ear
Middle ear
Inner ear
conducting structures in all parts
sensory structures in inner ear
External ear
Pinna: elastic cartilage
External auditory meatus: lined by Skin with hair and wax Glands
Ear drum: Epidermis, middle CT, simple cuboidal pithelium
Middle ear
eardum to oval windwo with ossicles (malleus, incus, stapes)
tympanic cavity (simple squamous) Eustachian tube (pseudostratified) Mastoid sinuses (simple squamous)
Vestibulocochlear apparatus
- in inner ear
- bony Labyrinth
- membranous labyrinth
Development of the external ear
- Ectoderm (1st pharyngeal groove) –> Epithelium of external auditory meatus
Development of the middle ear
- Endodern (1st pharyngeal pouch) –> Epithelium of the cavities of the middle ear
Development of inner ear
- ectodermal thickening –> PLACODA OTICA –> FOVEA OTICA –> VESICULAR OTICA
- Vesicula otica separates from ectoderm and forms sensoepithelium of membranous Labyrinth
- head Mesenchyme: all CT of the ear
The two Labyrinths of inner ear
Bony Labyrinth: within temporal bone, filled with perilymph and loose CT
Membranous Labyrinth: filled with endolymph, simple squamous and sensoepithelium
Parts of bony labyrinth
- semicircular canals
- vestibule
- cochlear canal
Parts of membranous labyrinth
Semicircular ducts
Utricle and saccule
Cochlear duct
Perilymph
- inside bony Labyrinth
- like ECM
- high NA, low K
Endolymph
- inside membranous Labyrinth
- like intracellular fluid
- low Na, high K
- produced by Stria vascularis
Sensory Region of membranous labyrinth
3 Cristae ampullares in semicircular ducts
2 maculae in saccule and utricle
1 organ of Corti in cochlear duct
Cell types of sensoepithelium
Specialized sensory cells (hair cells)
Supporting cells
Supporting cells in sensoepithelium
on b.m.
support
Nutrition
production of gelatinous material
Sensory hair cells in sensoepithelium
on supporting cells
Type I (goblet) Type II (columnar)
Basic part connects with nerve Fiber
Apical part has stereocilia and kinocilia
Stereocilia of sensory hair cell
- Long microvilli with actin cores
- immotile
Kinocilium of sensory hair cell
- motile
- Arrangement of microtubules
Crista ampullaris
- in ampulla of each semicircular canal
- ducts are lined by simple squamous Epithelium
- where membranous and bony Labyrinths fuse
- supporting and hair cells (type I and type II)
- stereocilia and kinocilia are covered by GELATINUOUS CUPULA
How does the crista ampullaris work?
sensroy Region of angular acceleration!
- when head is turned, endolmyph lags behind causing degletcion of gelatuínous cupula
- ->hyperpolarization or depolarization of hair cell
- -> excitation or Inhibition
- ->Excitation of the dendrite
- -> Impulse to the CNS
Macula
- sensoepitheliulm in utricle and saccule
- utricle and saccule are lined by simple squamous
- supporting cells
- hair cells (type I and type II)
How does the Macula work?
- Crystals of Calcium Carbonate make otoliths
- connected by proteins
- can detect gravity and linear acceleration
- ->movement of stereocilia and kinocilia
- ->excitation or Inhibition of hair cell
- ->Impulse to dendrite and CNS
Innervation of vestibular sense organs
hair cells are innervated by bipolar sensory Neurons
bodies of Neurons are in vestibular ganglion
Cochlea
- cochlear canal around modiolus
- three spiraling compartments:
1. Scala vestibuli with perilymph
2. Scala media with endolymoh
3- Scala tympani with perilymph
Scala vestibuli makes u turn at helicotrema and travels down to Scala tympani
Scala media walls
reissner’s membrane
Stria vascularis
Basilar membrane
Reissner’s membrane (vestibular membrane)
- between Scala media and Scala vestibuli
- simple squamous
- fibrous CT
- simple squamous
Stria vascularis
- pseudostratified
- produces endolymph and regulates ion transport
Basilar membrane
- supports organ of Corti
- Collagen fibers and simple squamous
Inner Corner of cochlear duct
spiral Limbus –> produced tectorial membrane
Tectorial membrane
- gelatinous
- similar to cupula or otolithic membrane
- covers stereocilia
Organ of corti
in Scala media
- sensory hair cells
- supporting cells
look at drawing!!!!
Inner tunnel (tunnel of Corti)
- surrounded by inenr and outer pillar cells
Sensory hair cells in organ of corti
- inner hair cells (1 row) –> type I cells
- Outer hair cells (3-5 rows) –> type II cells
- stereocilia that insert into tectorial membrane
- stereocilia are displaced during Vibration
- don’t have kinocilium!!!!
Phalangeal cells
- in organ of Corti (supporting cells)
- has apical phalangeal process
- forms reticular plate
- below reticular plate: corticolymph
- to stabilize
- tight junctions to maintain ion gradient
Innervation of cochlea
hair cells are innervated by bipolar sensory Neurons
Bodies are in spiral ganglion
Spiral (cochlear) ganglion
- cell bodies of bipolar Neurons wrap around modiolus
- axons come together as cochlear nerve in Center of modiolus
Sound transduction
tympanic membrane ossicles oval window perilymph in Scala vestibuli round window sensory hair cells basilar membrane
Taste buds
not in filiform papillae
- in stratified non-keratinized Epithelium
also in palate, Pharynx, Epiglottis and other parts of oral mucosa
Structure of a taste bud
Barrel shaped
Opening at Surface via taste port
contains sensoepithelium
Cell types in taste bud
- gustatory cells
- supporting cells
- Basal cells
Gustatory cells in taste bud
- spindle- shaped
- Long microvilli extendnig into pore
Basal cells in taste buds
- near b.m.
- precursors
Basic tastes
Sweet Salty Sour Bitter Unami
